package cc.laop.utils;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.security.MessageDigest;

public class AESUtil {
    /**
     * AES加密
     *
     * @param datasource 需要加密的数据
     * @param password   秘钥
     * @return 加密后的密文
     */
    public static String encrypt(String password, String datasource)
            throws Exception {
        byte[] rawKey = getRawKey(password);
        byte[] result = encrypt(rawKey, datasource.getBytes());
        return toHex(result);
    }

    /**
     * AES解密
     *
     * @param datasource 需要解密的数据
     * @param password   秘钥
     * @return 解密后的明文
     */
    public static String decrypt(String password, String datasource)
            throws Exception {
        byte[] rawKey = getRawKey(password);
        byte[] enc = toByte(datasource);
        byte[] result = decrypt(rawKey, enc);
        return new String(result);
    }

    private static byte[] getRawKey(String password) throws Exception {
        byte[] hash = MessageDigest.getInstance("MD5")
                .digest(password.getBytes("UTF-8"));
        return hash;
    }

    private static byte[] encrypt(byte[] rawKey, byte[] datasource)
            throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(rawKey, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        byte[] encrypted = cipher.doFinal(datasource);
        return encrypted;
    }

    private static byte[] decrypt(byte[] rawKey, byte[] encrypted)
            throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(rawKey, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        byte[] decrypted = cipher.doFinal(encrypted);
        return decrypted;
    }

    public static String toHex(String txt) {
        return toHex(txt.getBytes());
    }

    public static String fromHex(String hex) {
        return new String(toByte(hex));
    }

    public static byte[] toByte(String hexString) {
        int len = hexString.length() / 2;
        byte[] result = new byte[len];
        for (int i = 0; i < len; i++)
            result[i] = Integer
                    .valueOf(hexString.substring(2 * i, 2 * i + 2), 16)
                    .byteValue();
        return result;
    }

    public static String toHex(byte[] buf) {
        if (buf == null)
            return "";
        StringBuffer result = new StringBuffer(2 * buf.length);
        for (int i = 0; i < buf.length; i++) {
            appendHex(result, buf[i]);
        }
        return result.toString();
    }

    private final static String HEX = "0123456789ABCDEF";

    private static void appendHex(StringBuffer sb, byte b) {
        sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
    }

}
